Initial attempts at boosting magnetic hard-drive performance with a dose of flash memory fell flat; these so-called hybrid hard drives, released by Seagate and, in smaller quantity, by Samsung, didn't deliver on their promised speed gains. Now, nearly three years later, the concept of the hybrid drive gets new life, with the Seagate Momentus XT, the second generation of hybrid drive that mixes flash and hard disk. But does this drive deliver a measurable performance boost over its standard hard-disk cousins?

To answer that question, we ran the drive through a comprehensive round of tests. And we found that, unlike its predecessor, the Seagate Momentus XT drive actually does show significant performance improvements, improvements that put it ahead of standard hard drives, but still short of flash-based solid-state drives (SSD).

However, the Seagate Momentus XT hybrid drive gains an advantage by coming in at a lower cost and higher capacity than an SSD. Seagate's hybrid drive costs £115 for 500GB, and £95 for 320GB - far less than a straight-up solid-state drive.

Seagate Momentus XT: Second Time Lucky

The Seagate Momentus XT is a 2.5-inch, 7200 rpm drive that fits into a standard 9.5mm z-height drive slot. The drive comes in 320GB and 500GB; each of these uses two disk platters to achieve its areal density. Also inside: 4GB of flash memory, up from the paltry 256MB integrated into the company's first attempt at a hybrid drive.

Another difference: Where Seagate's first hybrid hard drive required operating system support (which was lacking in full at the time it came out), the Seagate Momentus XT achieves its performance independently of the operating system, and of the motherboard, too, according to Seagate. The drive is designed to boost read performance, but it will also help write performance, too.

Improved specs and engineering can sound great on paper, but does the Seagate Momentus XT deliver? We tested the 500GB model against an SSD drive (the OCZ Summit Series 120GB), a 5400-rpm 2.5-inch drive (the Western Digital Scorpio Blue 750GB), and a 7200-rpm 2.5-inch drive (the Western Digital WD3220BEKT) to see how the hybrid drive compares. Before we began testing, Seagate warned us that, due to the architecture of the drive, we shouldn't expect to see the maximum benefits of flash integration on the first few test passes (typically, we run three timed passes for every test we perform). Instead, the Momentus XT would show its true performance colours, consistently, at between passes four through six. For that reason, we ran all four drives through seven passes on all of our tests.

In terms of raw performance, the SSD unsurprisingly led the pack: It had the fastest boot time and the fastest times on our file read and copy tests. In second came the Momentus XT: It fell somewhere between the SSD and the 7200-rpm drive.

On our boot-up tests, the SSD took 86 seconds. That compared to the 110 seconds for the Momentus XT hybrid, 149 seconds for the 7200-rpm drive, and 159 seconds for the 5400-rpm drive. As Seagate indicated, not until pass number three did the drive begin to show stable, consistent results.

The Momentus XT consistently outpaced the 7200-rpm drive on our performance tests, typically almost precisely between the SSD and the 7200-rpm drive. For example, on our read 3.7GB of files test, the SSD required 26.7 seconds to complete the task, the hybrid drive 40.4 seconds, and the 7200-rpm drive 54.4 seconds (the 5400-rpm drive was just a little farther behind, at 54.4 seconds.

The hybrid drive performed similarly relative to the SSD and the 7200-rpm drive when it came to our write 3.7GB of files test. There, the hybrid drive logged 44.6 seconds, compared with the SSD's 25.2 seconds, the 7200-rpm's 61.5 seconds, and the 5400-rpm's 125.5 seconds.

The differences were less pronounced for the malware scan; there, the hybrid drive and 7200-rpm drive performed comparably, with the SSD leading the way. Ditto with regard to our PC WorldBench 6 tests; there, the system with the hybrid drive performed comparably to the 7200-rpm drive (scoring 130 for the hybrid drive, and 129 for the 7200-rpm); by comparison, the system with the SSD scored 139, and the system with the 5400-rpm drive scored 125.

SHOULD I BUY SEAGATE MOMENTUS XT?

For now, the Seagate Momentus XT is a lone duckling in a sea of options. But now that the drive has proven itself, it will be interesting to see if other drive makers decide to go the route of hybrid technology. If sheer performance is what you want, SSD remains king. But it also remains expensive, and limited in capacity. But if you want a performance boost on a budget, and you value capacity too, this second-gen hybrid drive makes a good compromise.